Doctors have long known that the sooner a stroke is treated, the better the outcome. But now a new study finds just how much each minute counts.

For each 15-minute head start doctors get on treating stroke, they cut the risk of stroke symptoms and death by 4 percent, according to the study of more than 58,300 ischemic stroke patients published Tuesday in the Journal of the American Medical Association. What’s more, every 15 minutes also improves how you leave the hospital, with a 4 percent increased likelihood of walking out and a 3 percent increased chance of heading home instead of going to a rehab center or nursing home.

A stroke is a major reduction in the normal flow of blood to the brain. A person dies from stroke every four minutes in the U.S., according to the U.S. Centers for Disease Control and Prevention — that’s almost 130,000 Americans each year, making strokes one of the leading causes of death in the country. More than half of stroke survivors age 65 and older lose the ability to walk.

This new study is 30 times larger than the latest trials that evaluated stroke treatment, factoring in data from nearly 1,400 hospitals — and not only large academic hospitals but community medical centers as well. In other words, these findings are more likely to be what the average American experiences.